JP3447975B2 - Switching power supply circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] The present invention relates to a method for controlling a plurality of output voltages.
Switching power supply to obtain
While maintaining a high degree of accuracy, to prevent equipment
About technology. [0002] 2. Description of the Related Art In recent years, electronic devices have many devices inside.
Equipped with functional circuits and devices, and should be supplied to these functional circuits and devices.
It is natural that the driving voltage becomes two or more types (voltage values)
It became like. To obtain multiple voltages with different voltage values
Has, for example, as many power supply circuits as required for that voltage
The use of a power supply is also conceivable. But the power times
As the number of roads increases, the cost increases and the shape increases.
There is a problem. Therefore, the power supply built into the electronic equipment
The device has multiple outputs with different voltage values from one power supply circuit.
Multi-output type switching power supply circuit that can obtain input voltage
Is often used. Such a multi-output switch
As an example of the switching power supply circuit, FIG.
There is a switching power supply circuit having a configuration as shown in FIG. [0003] The circuit shown in FIG.
Switching transistor Q1 between terminal 1 and ground
Main current path and the primary winding N5 of the transformer T3 are connected in series.
And a control circuit at the base of the switching transistor Q1.
4 is connected. Note that the ground is the reference voltage of the circuit shown in FIG.
Input terminal on the low potential side and each output on the low potential side.
Force terminals are not shown, but are connected to ground
Shall be. Filter between input terminal 1 and ground
Is connected. Secondary winding of transformer T3
One end of N6 is connected to ground, and the other end is connected to a diode D1.
Connected to the first output terminal 2 through the first output terminal 2
The capacitor C2 is connected to the ground. Secondary winding
The tap CT provided at a predetermined position of N6 is a diode D
2 to the second output terminal 3 and the second output terminal
A capacitor C3 is connected between 3 and ground. Soshi
Between the first output terminal 2 and the ground.
A resistor R1 and a resistor R2 are connected in series.
And the voltage signal appearing at the connection point of R2 is supplied to the control circuit 4.
Circuit configuration. [0004] In the circuit of FIG.
A switching transistor according to the drive signal output from the control circuit 4
The transistor Q1 repeats on and off operations. Then this
As a result, an alternating voltage is generated in the secondary winding N6 of the transformer T3.
Live. The alternating voltage that appears in the entire secondary winding N6 is
Rectified and smoothed by the resistor D1 and the capacitor C2.
The first output voltage V is located at the position of the first output terminal 2._O1H
Appears. Also, the second order divided by the tap CT
The alternating current appearing in the winding area n62 on the ground side of the winding N6
The pressure is rectified by the diode D2 and the capacitor C3,
The second output terminal 3 at the position of the second output terminal 3.
Force voltage V_O2LAppears. Here, the first output voltage V
_O1HAnd the second output voltage V_O2LAre both secondary windings
It is obtained from the flyback voltage that appears at N6. That
Therefore, the first output voltage V obtained from the entire secondary winding N6
_O1HIs the second output obtained from a part of the secondary winding N6.
Voltage V_O2LWill be higher. [0005] By the way, it appears at the connection point of the resistors R1 and R2.
The first output terminal appearing at the first output terminal 2
Pressure V_O1HAnd the magnitude according to the voltage value. Some reason
Output voltage V_O1HFluctuates from the specified value
The control circuit 4 appears at the connection point of the resistors R1 and R2.
The pulse width of the drive signal is changed according to the voltage signal,
Ratio of the on / off period of the switching transistor Q1,
That is, the on-duty is changed. Switching tiger
When the on-duty of the transistor Q1 changes, the primary winding N
The flow rate per unit time of the current passing through 5 changes,
Energy transmitted from primary side to secondary side of transformer T3
-The amount changes. Then, the first output voltage V_O1HIs strange
Voltage value according to the amount of energy transferred
To restore the voltage value of A switch based on the magnitude of the output voltage as described above
Control of the switching operation, so-called feedback control
Therefore, the first output voltage V of the circuit shown in FIG._O1HIs
The voltage value is stabilized at a substantially specified value. The second
Output voltage V_O2LFor the first output voltage V_O1H
If the voltage value is stable at an almost constant value,
That is, the state of the external load connected to each output terminal
Condition and input voltage V_INAs long as the voltage does not change,
It will be stabilized at a constant value. [0007] A switch as shown in FIG.
The switching power supply circuit has a high voltage value in the entire secondary winding N6.
Side first output voltage V_O1HCircuit configuration
ing. Making such a switching power supply circuit
At times, it is quite obvious, but the secondary of the transformer T3
The winding N6 has the maximum voltage value among the output voltages to be obtained.
Determine the number of turns based on that. Then, the secondary winding N6 is high.
The number of turns must be increased to obtain the voltage
As a result, as a result, the transformer T3 becomes larger,
Undesired phenomenon such as an increase in the size of a power supply circuit or power supply
Will cause. In the circuit shown in FIG.
First output voltage V obtained from entire next winding N6_{O 1H}But
Due to the stability, the secondary winding from the theory of the voltage divider circuit
The second output voltage V obtained from a part of N6_O2LAlso stable
Be converted to However, actually, the second output voltage V_O2L
About the provisional instruction, the first output voltage V_O1HVoltage value
Even if stable, changes in various factors, especially large output current
The voltage value fluctuates due to sudden increase or decrease. This is
Coupling between the windings of the transformer T3 constituting the source circuit
However, the actual product is not perfect (coupling coefficient is 1.0).
And the electric resistance existing in each winding and winding area and the flow there
Current causes a voltage drop, which changes the current value.
Is considered to be the cause. for that reason,
The switching power supply having the circuit configuration shown in FIG.
When the load condition changes greatly, the feedback
Output voltage V for which the lock control is not performed._O2LNo electricity
There is a problem that high stability cannot be expected in the pressure value. Therefore
According to the present invention, the stability of each output voltage is high and the size of the device is large.
Aim to obtain a switching power supply circuit that can prevent
Target. [0009] SUMMARY OF THE INVENTION A switch according to the present invention.
Power supplyWith switching element on / off operation
The voltage value differs from the voltage generated in the secondary winding of the transformer.
Multi-output type switching
In the source circuit, when the switching element is off,
The first output is generated by the flyback voltage generated in the entire next winding.
When the voltage is obtained and the switching element is on, the secondary winding
Induced voltage and first output voltage generated in partial winding area of wire
The second output voltage having a higher voltage value than the first voltage.
Get pressure. Here, the first output voltage is a switching element.
And a control circuit connected to the control terminal of the switching element.
Characterized by being stabilized by a control system including
You. [0010] BEST MODE FOR CARRYING OUT THE INVENTION A tap provided at a predetermined position
Using a transformer having a secondary winding, the primary winding of the transformer
And a switching element in series between the input terminal and ground.
Connecting. Connect one end of the secondary winding of the transformer to the first rectifier
And the other end of the secondary winding is directly connected to
Connected to the first output terminal and provided at a predetermined position on the secondary winding
Tap to the second output terminal via the second rectifier
Connecting. A first capacitor is provided between the first output terminal and ground.
A second capacitor between the second output terminal and ground.
Circuit elements connected to each other. And the second
The first output voltage on the output terminal side of 1 is generated in the entire secondary winding
While the second output terminal
Side second output voltage by the secondary winding tap.
Of the induced voltage generated in one of the winding regions divided by
From the output terminal side. [0011] DESCRIPTION OF THE PREFERRED EMBODIMENTS The stability of each output voltage is high and the size of the device is large.
A switch according to the first embodiment of the present invention, which can prevent mold
FIG. 1 shows a circuit diagram of the switching power supply circuit. Times shown in FIG.
The road has the following configuration. Input terminal 1 and ground
Between the PNP type switching transistor Q1
The current path and the primary winding N1 of the transformer T1 are connected in series,
The control circuit 4 is connected to the base of the switching transistor Q1.
Connecting. One end of the secondary winding N2 of the transformer T1 is
Connected to the cathode of node D1 and its anode to ground.
Connecting. The other end of the secondary winding N2 is connected to the first output terminal 2.
Connect a capacitor C2 between the output terminal 2 and ground.
Continue. Further, between the output terminal 2 and the ground,
Connects a series circuit of resistors R1 and R2 as a pressure detection circuit
And controls the voltage signal appearing at the connection point between the resistors R1 and R2.
Input to Road 4. Provided at a predetermined position of the secondary winding N2.
Connect the tap CT to the anode of the diode D2,
The cathode of the diode D2 is connected to the second output terminal 3,
The capacitor C3 is connected between the input terminal 3 and the ground. 2
One end of the secondary winding N2 on the diode D1 side and its secondary winding
Switching of the primary winding N1 having the same polarity as one end of N2
Capacitor between one end of transistor Q1 sideC4Connect
Between the input terminal 1 and the ground.
The sensor C1 is connected. The circuit of FIG. 1 having such a configuration
The general operation of is as follows. First, a signal supplied from the control circuit 4 is used.
The switching transistor that was on
When the star Q1 is turned off, each winding of the transformer T1 is turned off.
The line indicates when the switching transistor Q1 is in the ON state.
Flyback voltage is generated by the energy stored in the
I do. Then, it is turned on with respect to the flyback voltage.
The entire secondary winding N2 via the diode D1
Generated flyback voltage is applied across capacitor C2
Is done. As a result, the capacitor C2 is charged, and the capacitor C2 is charged.
The voltage generated between the terminals of the sensor C2 is the first output voltage V
_O1LAt the position of the output terminal 2. In addition, steady
In the operating state, the first output voltage V_O1LIs the control circuit
4 and a feedback transistor including the switching transistor Q1.
It is stabilized by the clock control system. Next, according to a signal supplied from the control circuit 4,
The switching transistor Q1 is turned on.
Then, current flows into the primary winding N1 of the transformer T1, and
An induced voltage is generated in each winding of the lance T1. At this time, 2
Induction voltage generated in a part of the winding area n21 of the next winding N2
Is in the forward direction of the diode D2, and the winding region n
21 and the voltage across the capacitor C2
Is applied to the capacitor C via the diode D2.
3 will be applied to both ends. This allows condensate
The capacitor C3 is charged, and the voltage generated between the terminals of the capacitor C3 is charged.
Is the second output voltage V_O2HAt the position of output terminal 3
Appear. Then, according to a signal supplied from the control circuit 4,
Therefore, the switching transistor Q1 is turned off again.
And the above operation is repeated. The circuit of the present invention shown in FIG.
And the first output voltage V_O1LOccurred in the secondary winding N2
While obtaining from the flyback voltage, the second output voltage V
_O2HFor the induced voltage generated in the secondary winding N2 and the
1 output voltage V_O1LGet more. And the secondary winding N2
Output voltage V derived from tap CT of_O2Hof
Output voltage V obtained from the entire secondary winding N2_O1L
It is characterized by being higher. like this
In the switching power supply circuit of the present invention, the transformer
The specification of the secondary winding N2 of T1 such as the number of turns of the winding is a voltage.
The value is determined based on the lower output voltage. Secondary winding
If the voltage value of the output voltage to be obtained from the entire N2 is low,
It is not necessary to wind many wires, and the size of the transformer T1 is suppressed.
Can be obtained. As a result, switching power supply circuits and
It is possible to prevent an increase in the size of the power supply device. The circuit shown in FIG. 1 operates according to the flyback voltage.
The output voltage that is gaining energy is the first output voltage V
_O1LFor example, the first output terminal 2 side
Changes in the output current of the second output voltage V_O2HEvil
The effect can be reduced. In addition to this, the second output
Voltage V_O2HIs the first output voltage V_O1LAnd winding area n
21 is determined by the induced voltage. here,
First output voltage V_O1LIs controlled by feedback control.
The induced voltage is the same as that of the primary winding N1.
Turn ratio and input voltage V of line region n21_INDetermined by
And the input voltage V_INIs stable, the second output voltage V
_O2HAlso shows a stable value. As a result, the second output voltage
V_O2HIndicates high stability. If you enter
Voltage V_INChanges, the first output voltage V_O1LBut one
If constant, the second output voltage V_O2HIs limited
The second output voltage V _O2HConventional stability
This does not cause a situation that deteriorates as compared with the circuit of FIG. Although detailed description is omitted, FIG.
The capacitor C4 is used in a circuit having a configuration as shown in FIG.
Used in combination with capacitor C2. At this time,
The capacitor C2 and the capacitor C4 are the primary winding of the transformer T1.
The AC component of the voltage appearing at one end of the line N1 is converted from the primary side to the secondary side.
Side, and the magnetic force between the primary and secondary windings of the transformer T1.
Energy transfer separate from energy transfer by static coupling
Form means. This capacitor C4 is installed in the circuit.
Power supply circuit is more efficient than when it is not installed.
There are points. This capacitor C4 depends on the specifications of the power supply.
Is omitted. FIG. 2 shows a switch according to a second embodiment of the present invention.
The circuit diagram of the switching power supply circuit is shown. The circuit of FIG.
A switch whose input voltage is positive with respect to the ground potential
While the power supply circuit shown in FIG.
Switch where the output voltage is negative with respect to the ground potential
This constitutes a switching power supply circuit. Circuit shown in FIG.
Is substantially the second order of the transformer T1 of the circuit of FIG.
A transformer having a secondary winding N4 whose polarity is opposite to that of the winding N2.
Use the sense T2. And diodes D1 and D1
2. Connect the anode and cathode of the
The circuit configuration is such that the capacitor C4 is deleted. What
FIG. 2 shows the configuration of the other circuit parts of the circuit of FIG.
1 is the same as the circuit of FIG. In the circuit having such a configuration, first, the switch
The switching transistor Q1 is turned off, and the secondary winding N
4 generates a flyback voltage, the secondary winding N4
The flyback voltage generated throughout is applied to the capacitor C2
Is done. As a result, the capacitor C2 is charged and its end is charged.
The voltage generated between the terminals is the first output voltage V_O1LBecomes Next
The switching transistor Q1 shifts to the ON state
And an induced voltage is generated in the secondary winding N4, and a partial winding thereof is generated.
The induced voltage generated in the region n41 and the first output voltage V
_O1LIs applied to the capacitor C3.
You. As a result, the capacitor C3 is charged, and between its terminals
Is the second output voltage V_O2HBecomes In addition,
From the polarity of the secondary winding N4, the first output voltage V_O1LAnd the second
2 output voltage V_O2HMeans that the voltage value is
It will be a negative value. Thus, the circuit shown in FIG.
Has a voltage value opposite to the ground with respect to the ground,
The operation is substantially the same as that of the circuit. The present invention described above and shown in FIGS. 1 and 2
In the circuit according to the embodiment, two first and second output voltages are obtained.
Of the present invention applied to a switching power supply circuit for
However, the present invention is applied to a power supply device configured to obtain three or more output voltages.
The invention may be applied. In addition, in each embodiment,
In the circuit, the secondary winding is tapped and the secondary winding is
Divided into winding regions, and the induced voltage appearing in one winding region
We are using. But with primary, secondary and tertiary windings
Connecting a secondary winding and a tertiary winding using a transformer
A circuit corresponding to an embodiment of the present invention may be configured. [0021] As described above, the switch according to the present invention is
The switching power supply circuit connects one end of the secondary winding of the transformer to the first
Connected to the reference potential point via the rectifying element
End directly to the first output terminal, and
The tap provided at the second position is connected to the second
Connect to output terminal. With such a configuration, the first
The output voltage on the output terminal side of the
Output from the second output terminal while obtaining the
For the voltage, one divided by the tap of the secondary winding
Induced voltage generated in the winding area and output on the first output terminal side
It is characterized in that it is obtained from a combined voltage of voltages. According to the present invention as described above, the entire secondary winding
Output voltage to be obtained from
The transformer is not required to be large.
You. In addition, the first output is stabilized by feedback control.
The second output is obtained by the force voltage and the induced voltage generated in the secondary winding.
By obtaining the voltage, the output power with high stability
Pressure is obtained. As a result, the stability of each output voltage is high.
And a multi-output switch
A switching power supply circuit can be obtained.

[Brief description of the drawings] FIG. 1 shows a switching power supply according to a first embodiment of the present invention.
The circuit diagram of a source circuit. FIG. 2 shows a switching power supply according to a second embodiment of the present invention;
The circuit diagram of a source circuit. FIG. 3 shows a conventional multi-output type switching power supply circuit.
FIG. [Explanation of symbols] 1: input terminal 2: first output terminal 3: second
Output terminal 4: Control circuit C2: Capacitor
(First capacitance element) C3: Capacitor (second capacitance)
CT: Center tap D1: Die
Diode (first rectifier) D2: diode (second
N1 and N3: primary winding (first winding)
Line) N2, N4: secondary winding n21, n4
1: winding area (second winding) n22, n42: winding
Line region (third winding) Q1: Switching transistor
T (switching element) T1, T2: Transformer
    V _IN: Input voltage V_O1L: First output voltage
      V_O2H: Second output voltage

Claims (1)

(57) [Claim 1] A multi-output type switching power supply circuit for obtaining a plurality of output voltages having different voltage values from the voltage generated in a secondary winding of a transformer due to the on / off operation of a switching element. A first output voltage is obtained by a flyback voltage generated across the secondary winding when the switching element is in an off state;
A second output voltage having a higher voltage value than the first voltage due to the induced voltage generated in a partial winding region of the secondary winding and the first output voltage when the switching element is in an on state; Wherein the first output voltage is stabilized by a control system including the switching element and a control circuit connected to a control terminal of the switching element.